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. Author manuscript; available in PMC: 2017 Dec 2.
Published in final edited form as: Org Lett. 2016 Nov 18;18(23):6188–6191. doi: 10.1021/acs.orglett.6b03246

Figure 2.

Figure 2

(A) Orthogonal protecting groups on a (methyl)lanthionine building block (DL-MeLan here) allow elongation and subsequent cyclization of a peptide. For alternative protecting group schemes, see 10 (B) Introduction of short oligopeptides containing dehydro amino acids (Dhx). (C) If the amine coupling partner for cyclization is a dehydro amino acid (Dha here), the low reactivity of the enamine promotes hydrolysis to the ketone preventing cyclization.